The present invention relates to the field of detection of parameters of a remote device and more particularly to a method of determining the value of a resistive element in a remote device, and in response to the determined value either determining parameters based on one or more resistive values or determining parameters from a memory unit on the remote device.
The growth of local and wide area networks based on Ethernet technology has been an important driver for cabling offices and homes with structured cabling systems having multiple twisted wire pairs. The ubiquitous local area network, and the equipment which operates thereon, has led to a situation where there is often a need to attach a network operated device for which power is to be advantageously supplied by the network over the network wiring. Supplying power over the network wiring has many advantages including, but not limited to; reduced cost of installation; centralized power and power backup; and centralized security and management.
Several patents addressed to this issue exist including: U.S. Pat. No. 6,473,608 issued to Lehr et al., and U.S. Pat. No. 6,643,566 issued to Lehr et al., the entire contents of both of which are incorporated herein by reference. Furthermore a standard addressed to the issue of powering remote devices over an Ethernet based network, known as Power over Ethernet (PoE), has been published as IEEE 802.3af-2003, whose contents are incorporated herein by reference.
The above standard describes two alternative arrangements for powering from power sourcing equipment (PSE), denoted Alternative A and Alternative B. Alternative A is also known as data pair powering, in which power is supplied on wire pairs carrying data. Alternative B is also known as spare pair powering, in which power is supplied on wire pairs not used for carrying data. Since it is possible that two separate PSEs, one that implements Alternative A and one that implements Alternative B, may be attached to the same link segment a back off algorithm having different detection back off times for Alternative A and Alternative B are defined. Thus, in order to be in compliance, the PSE must be supplied with information indicating whether it is arranged according to Alternative A or Alternative B.
U.S. patent application Ser. No. 10/334,386 to Elkayam et al, published May 29, 2003 as US 2003/0099076 A1, whose entire contents are incorporated herein by reference, is addressed to an integral board and module for Power over LAN. Power over LAN has the same meaning throughout this application as PoE. The Power over LAN support circuitry which couples the approximately 48V DC current controlled power to the communication cabling via connectors is located on a board separate from the module comprising the power distribution and control circuitry. No means of automatically supplying the power distribution and control circuitry with information regarding Alternative A or Alternative B of the support circuitry is described.
What is therefore needed, and not known in the prior art, is a means for supplying configuration information from a remote site comprising support circuitry coupling power into communication cabling to power sourcing equipment.